• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.5
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• pp.50-57
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• 2016

The present study proposed three inspection reliability indices which compared inspection results evaluated at in-depth(routine) inspection and in-depth safety inspection; Nominal inspection reliability index, Real inspection reliability index, and DS nominal inspection reliability index. The methods to improve the inspection reliability were also proposed. Since bridge inspection process is critical to ensuring the safety of bridges and identifying repair and maintenance needs, the quality of the inspection data produced from the inspection process is very important. Consequently, the inspection reliability indices were suggested to evaluate quality of current inspection practices. Specifically, approximately 85% of inspection errors evaluated by the DS nominal inspection reliability index are within 1 rating grade(equal to or less than damage score ${\pm}0.1$). In order to improve the inspection reliability, transportation agency should implement QC(Quality Control) practices and develop professional expertises of inspectors by higher requirements for inspectors, on-off line inspection training and etc.

• Journal of the Korea Institute of Building Construction
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• v.15 no.2
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• pp.185-192
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• 2015

Expansion joint is the essential element of the bridge in many cases. When the bridge faces chloride of preventing freezing on the surface of the bridge, the expansion joints is damaged significantly, thus this reduces service life and increases maintenance cost of the bridge. As a solution of this problem, new technology using high ductile materials for the joint without expansion joint was developed and in this research, crack control performance, preventing leaking after the cracking, and chloride resistance were experimentally evaluated. As a result of the experiment, with PCM and FRC materials, the connecting joint suffered poor crack dispersion and severe damage by the chloride penetration while with high-ductile material, the connecting joint dispersed the tensile deformation to microcracks stably up to 7.5mm. Furthermore, under the sever conditions, the leaking was prevented and penetration of chloride ions was prevented after the crack occurred.

• Journal of the Korean Society of Marine Environment & Safety
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• v.7 no.3
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• pp.17-28
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• 2001

The wheelhouse front glass of a Fore-Bridge-Ship (Ro-Ro Ship) was broken by the shipping of water in rough seas, and then the flooding of seawater into the wheelhouse caused the uncontrollable condition of the ship. The hull which was entered into the floating condition rolled severely, and the heavy rolling caused secondary damage such as the collapse of a lot of cargo. It was an incredible accident because the height of bow freeboard was about 2.5 times higher than the standard height of minimum bow freeboard regulated by the International Load Line Convention(1966). And it would be also difficult for navigators to imagine a great deal of seawater flooding into the wheelhouse because the front glass was positioned at about 20m height above the sea surface. In this paper, we carried out the evaluation for the safety navigation of the Fore-Bridge-Ship numerically against ship's speed and encountering angle to the wave in each sea state of rough sea, by using the integrated seakeeping performance index (ISPI) which is able to evaluate synthetically the safety operation of ships. And then the problem on the application of the past criteria proposed as the safety navigation of a merchant ship was clarified by inquiring the dangerousness of the shipping of water at her bow deck, which caused the breakage of the wheelhouse front glass.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.1
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• pp.117-124
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• 2010

Different to other social infrastructures, bridge elements or bridges can be damaged or collapsed and this may cause death toll and severe social and economical damage, bridges should be managed to maintain a safety level. Diverse strengthening methods is developed to improve a deteriorated bridge performance up to original design level. But rational decision-making process and methodologies to select a optimum strengthening method are absence yet in Korea. This paper therefore derived items and proposed methodologies for quantity estimate considering uncertainty to select a optimum strengthening method among conceptually designed alternatives. And also, to demonstrate the applicability and verification of the proposed approach, it was applied to select the optimum strengthening method for the deteriorated T-shape concrete girder bridge. The model and the procedure can greatly contribute to the uncertainty-oriented alternative selection.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.39 no.1
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• pp.135-146
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• 2019

In this paper, the preventive maintenance strategy in operation stage of a bridge using Bayesian inference is proposed. The proposed technique can be used to predict the variation in the performance (or condition) of the bridge with higher accuracy, considering the uncertainty of monitoring. The applicability of the proposed method to the existing bridges is verified and analyzed that have an advantage in terms of maintenance cost efficiency compared to the conventional periodic maintenance system, which establishes maintenance after damage. It is expected that the proposed preventive maintenance method can be used to overcome the limitation of the conventional periodic maintenance method and to make practical bridge maintenance decision.

• Journal of the Korea Society of Computer and Information
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• v.26 no.8
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• pp.139-147
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• 2021

In this study, we proposed the possibility of reliability analysis of risk index by using Monte Carlo simulation as basic data of safety accident occurrence data and expert opinion by construction industry type. Through this, it is expected that risk index for safety accidents according to detailed types of works will be presented stochastically and it will be possible to predict the risk factors and the expected range of damage based on the reliability analysis in the construction safety management plan. It will also reduce many of the planning risks that are common to decision makers in the field of construction management. In identifying risks, road bridge construction was classified into earthworks, drainage works, and bridge construction, and possible safety accidents were classified based on expert data. The risk index was calculated for each detailed construction of road and bridge construction, drainage construction, and bridge construction.

• Journal of Korean Society of Disaster and Security
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• v.15 no.4
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• pp.31-38
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• 2022

In the case of special bridges whose superstructure is supported by cables, there are many blind spots that are difficult to access without special equipment and personnel. As a result, there are difficulties in the safety inspection of special bridges. The purpose of this study is to review the inspection blind spots of cable-supported bridges such as cable-stayed bridges and suspension bridges, and to study ways to eliminate blind spots using drones. To this end, the cables, stiffened girder, and pylons of the cable-stayed bridge located in the sea were inspected using drones. Through this study, it was confirmed that external safety inspection of special bridges that are difficult for inspectors to access is possible using drones. In particular, drone inspection to check the external condition and damage of the pylon, which is a blind spot for inspection of special bridges, is a very effective safety inspection method.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.3A
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• pp.383-390
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• 2008

A Precast Prefabricated Bridge Column using steel tube and prestressing bar was proposed for the application of precast method on substructure. A column specimen designed by the proposed bridge column system was made and performed a quasi-static test. The failure mode appeared to be a flexural failure and there is no damage on column segment connection. And it is good use of the self-centering ability by prestressing force. Test results showed that a column specimen satisfy the earthquake specification, and the structural stability was verified. Nonlinear finite element analysis was performed and compared with the test results. Force-displacement relation and location of crack from the analysis results were compared with the test results and it agreed well. The quantitative analysis was also performed by a parametric study using this modeling technique.

• Smart Structures and Systems
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• v.33 no.3
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• pp.189-199
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• 2024

To properly extract the strain components under varying operational conditions is very important in bridge health monitoring. The abnormal sensor readings can be correctly identified and the expected operational performance of the bridge can be better understood if each strain components can be accurately quantified. In this study, strain components under varying load conditions, i.e., temperature variation and live-load variation are evaluated based on field strain measurements collected from a real concrete box-girder bridge. Temperature-induced strain is mainly regarded as the trend variation along with the ambient temperature, thus a smoothing technique based on the wavelet packet decomposition method is proposed to estimate the temperature-induced strain. However, how to effectively extract the vehicle-induced strain is always troublesome because conventional threshold setting-based methods cease to function: if the threshold is set too large, the minor response will be ignored, and if too small, noise will be introduced. Therefore, an autoencoder framework is proposed to evaluate the vehicle-induced strain. After the elimination of temperature and vehicle-induced strain, the left of which, defined as the model error, is used to assess the operational performance of the bridge. As empirical techniques fail to detect the degraded state of the structure, a clustering technique based on Gaussian Mixture Model is employed to identify the damage occurrence and the validity is verified in a simulation study.

• Steel and Composite Structures
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• v.50 no.6
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• pp.659-674
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• 2024

Casting Ultra High-Performance Concrete (UHPC) on an orthotropic steel deck and forming a composite action by connectors could improve the steel deck fatigue performance. This study presents the mechanical performance of a proposed post-combination connection between UHPC and steel, which had a low constraint effect on UHPC shrinkage. A total of 10 push-out tests were conducted for static and fatigue performance investigations. And the test results were compared with evaluation methods in codes to verify the latter's applicability. Meanwhile, nonlinear simulation and parametric works with material damage plasticity models were also conducted for the static and fatigue failure mechanism understanding. The static and fatigue test results both showed that fractures at stud roots and surrounding local UHPC crushes were the main failure appearances. Compared with normally arranged studs, group arrangement could result in reductions of static stud shear stiffness, strength, and fatigue lives, which were about 18%, 12%, and 27%, respectively. Compared with the test results, stud shear capacity and fatigue lives evaluations based on the codes of AASHTO, Eurocode 4, JSCE and JTG D64 could be applicable in general while the safety redundancies tended to be smaller or even insufficient for group studs. The analysis results showed that arranging studs in groups caused obviously uneven strain distributions. The severer stress concentration and larger strain ranges caused the static and fatigue performance degradations of group studs. The research outcome provides a very important basis for establishing a design method of connections in the novel post-combination steel-UHPC composite deck.